always call WebPInitSamplers(), don't try to be smart
always call WebPInitSamplers(), don't try to be smart

if FANCY_UPSAMPLING was not defined but io->fancy_upsampling was set,
then the call to WebPInitSamplers() was skipped -> boom.

Change-Id: Id63e2ecc09f532fbe2ec9936d9ce4b502ba8fac5

redengineer/libwebp,PKRoma/libwebp,redengineer/libwebp,ttyangf/libwebp,redengineer/libwebp,ttyangf/libwebp,ttyangf/libwebp,PKRoma/libwebp,webmproject/libwebp,ttyangf/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp,ttyangf/libwebp,redengineer/libwebp,PKRoma/libwebp,webmproject/libwebp,redengineer/libwebp,PKRoma/libwebp